Will JJ 6V6s take more abuse than some NOS?

[Leonc]

Seems like I read somewhere that JJ6V6 will stand up to a good deal of abuse (e.g. that they can be biased hotter) than many NOS 6V6s. Anyone know of any evidence to support this?

[Trout]

Seems like I read somewhere that JJ6V6 will stand up to a good deal of abuse (e.g. that they can be biased hotter) than many NOS 6V6s. Anyone know of any evidence to support this?


I have been running a pair in a PP amp at 465V anode, 415V screen, 21ma fixed bias into a 6600 ohm OT for about 2 months now without a hint of redpate or failure. They actually sound great in the upper voltage ranges, though I have not tried to reach the meltdown area yet.

Trout

[Tripower455]

I ran a pair in my Hiwatt DR504 at 470 on the plates, and they held up fine for about a hundred hours of use. I pulled them out and rebiased a pair of EL34s in it so I could use it as a backup for a gig.

They sounded great in there btw!

[JJman]

At one point during my recent build I powered up after disconnecting the trem, not realizing it was also the DC ground reference for the 6v6s' grids. So the (cathode biased) idle drifted up up and away making the cathode resistor very hot. :FM I couldn't believe the voltage reading on it until I touched the ceramic. OUCH!

I don't know the exact figure but I estimated that each was running about 20+ watts for some time on the bench. No red spots on plates at the time and they are working great and are still matched.

[slider313]

I have been running a pair in a PP amp at 465V anode, 415V screen, 21ma fixed bias into a 6600 ohm OT for about 2 months now without a hint of redpate or failure. They actually sound great in the upper voltage ranges, though I have not tried to reach the meltdown area yet.

Trout

Do you think a pair of NOS Brimars or RCA's would hold up under those conditions?
Also,have you tried this with the new Tung Sol 6V6?

[Trout]

Do you think a pair of NOS Brimars or RCA's would hold up under those conditions?
Also,have you tried this with the new Tung Sol 6V6?


I really have my doubts on those ones, I was never able to get as much life with NOS tubes in these upper ratings. Not saying it can not be done, but JJ's exceed the normal 6V6 spec by a lot. I have not tested the new Tung-sol yet but I suspect they would not be any better than the other 6V6's by New Sensor (EH6V6).

YMMV but not by much.

[Blue Strat]

Not sure why you'd run 6V6s that far outside of spec, but Brimars have worked in Jim Kelly amps with 500V on the plates. The original Kelly's shipped with JAN Philips 6V6s.

[Trout]

Not sure why you'd run 6V6s that far outside of spec, but Brimars have worked in Jim Kelly amps with 500V on the plates. The original Kelly's shipped with JAN Philips 6V6s.

I guess they must not be that far out of spec if Jim Kellys been doing the same thing huh?

It has been my experience that " JJ 6V6's" do indeed run with great success in both HIFI and guitar gear at voltages in excess of 450V.

A lot of guys also use them in Marshalls intead of EL34's with proper bias mods and adjustments.

I feel they are much closer to 6L6's than 6V6's.

[Blue Strat]

I guess they must not be that far out of spec if Jim Kellys been doing the same thing huh?

.

The tube spec's are on paper and don't change on the whim of an amp "designer". The fact that they work indicates that these particular tubes, and possibly others, work beyond the published spec.

One thing often missed in these discussions is how solid the power supply in the amp is. If it sags, it's easier of the tubes because as current goes up, plate voltage comes down.

JJ "6V6s" may be more robust than NOS, but this only proves that they're not real 6V6s. This is neither good nor bad, just a statement of fact.

[Tripower455]

The tube spec's are on paper and don't change on the whim of an amp "designer". The fact that they work indicates that these particular tubes, and possibly others, work beyond the published spec.

One thing often missed in these discussions is how solid the power supply in the amp is. If it sags, it's easier of the tubes because as current goes up, plate voltage comes down.

JJ "6V6s" may be more robust than NOS, but this only proves that they're not real 6V6s. This is neither good nor bad, just a statement of fact.


I agree......

The JJs are built differently than real, NOS 6V6s and hold up.......

[mark norwine]

One thing often missed in these discussions is how solid the power supply in the amp is. If it sags, it's easier of the tubes because as current goes up, plate voltage comes down.

Bingo. VA curve of the PT is the key.

Nobody ever seems to want to discuss this aspect of amp design....

('cept for me & Mike...)

[Trout]

The tube spec's are on paper and don't change on the whim of an amp "designer".

That's true, to a point.

It seems that the TV/Radio & Audio specs on sheets do not parallel what was and is common guitar amp design practices. Even as far back as the early 50's.
So that pretty much makes some/most of the old data sheets incomplete as far as actual capability or what would be considered normal practices.

[Blue Strat]

That's true, to a point.

It seems that the TV/Radio & Audio specs on sheets do not parallel what was and is common guitar amp design practices. Even as far back as the early 50's.
So that pretty much makes some/most of the old data sheets incomplete as far as actual capability or what would be considered normal practices.

Agreed, the specs are conservative. But I think you'll agree that even though something that's supposed to have a max of 350V and works at least to 420V probably won't work at 1000 volts, right? So, what's to say that it will work at 450, 460, etc?

Using an example of one, 10 or 100 isn't necessarily proof that they'll ALL work.

[Trout]

Agreed, the specs are conservative. But I think you'll agree that even though something that's supposed to have a max of 350V and works at least to 420V probably won't work at 1000 volts, right? So, what's to say that it will work at 450, 460, etc?

Using an example of one, 10 or 100 isn't necessarily proof that they'll ALL work.


Oh, I agree about NOS tubes, but the OP was specifically about JJ tubes which are rated up to 500V which we both agree are entirely different animals.

Personally, as far as NOS goes, I would not trust anything at extreme voltages except for maybe a few various brand 6V6GTA's

[Blue Strat]

One piece of information missing in the OP's post, and there's almost ALWAYS something important missing, is what amp he's thinking about and/or why he's posing this question.

In addition, he mentions "biasing hotter", nothing at all about higher plate voltage.

[Trout]

One piece of information missing in the OP's post, and there's almost ALWAYS something important missing, is what amp he's thinking about and/or why he's posing this question.

In addition, he mentions "biasing hotter", nothing at all about higher plate voltage.


Good Call ,

my read on it was just more abuse in general, and of course he has not responed further in the thread leaving us all guessing as to his intent.

[Bonenut]

I haven't been able to kill a pair of RCA GTY's with 450 anode, 445 screen...

[Blue Strat]

I haven't been able to kill a pair of RCA GTY's with 450 anode, 445 screen...

Same here. I haven't been able to kill NOS ANYTHING (6V6) at those voltages in a Deluxe Reverb. Of course, the wimpy DR power supply is a factor as it sags in a big way when you get crankin'. ;)

[HipKitty]

Not sure why you'd run 6V6s that far outside of spec, but Brimars have worked in Jim Kelly amps with 500V on the plates. The original Kelly's shipped with JAN Philips 6V6s.

Man! I love those Kelly's!